问题
So,
After upgrading our prject to Qt5 we are experiencing issues with glew. The app links a library that needs glew to work, and that works fine when using the library in non Qt apps.
Now though we are linking the library into a qt app and rendering into a glwidget. This used to work but now it doesnt. We get a huge array of errors that mostly say "redefinition of" something. Here's some examples:
1>c:\glew-1.9.0\include\gl\glew.h(275): error C2371: 'GLdouble' : redefinition; different basic types
1> c:\qt\qt5.0.2\5.0.2\msvc2012_64\include\qtgui\qopengl.h(71) : see declaration of 'GLdouble'
1>c:\glew-1.9.0\include\gl\glew.h(630): warning C4005: 'GL_DOUBLE' : macro redefinition
1> c:\qt\qt5.0.2\5.0.2\msvc2012_64\include\qtgui\qopengl.h(68) : see previous definition of 'GL_DOUBLE'
1>c:\glew-1.9.0\include\gl\glew.h(1655): error C2371: 'GLintptr' : redefinition; different basic types
1> c:\qt\qt5.0.2\5.0.2\msvc2012_64\include\gles2\gl2.h(38) : see declaration of 'GLintptr'
1>c:\glew-1.9.0\include\gl\glew.h(1656): error C2371: 'GLsizeiptr' : redefinition; different basic types
1> c:\qt\qt5.0.2\5.0.2\msvc2012_64\include\gles2\gl2.h(39) : see declaration of 'GLsizeiptr'
1>c:\glew-1.9.0\include\gl\glew.h(1707): warning C4005: 'GL_BLEND_EQUATION_RGB' : macro redefinition
1> c:\qt\qt5.0.2\5.0.2\msvc2012_64\include\gles2\gl2.h(96) : see previous definition of 'GL_BLEND_EQUATION_RGB'
1>c:\glew-1.9.0\include\gl\glew.h(11533): warning C4005: 'GL_COVERAGE_SAMPLES_NV' : macro redefinition
You get the idea. Anyway how can I stop Qt including its gl stuff so glew can work by itself?
As you can see gles is being a problem, so I was directed to use this:
#define QT_NO_OPENGL_ES_2
But this has no effect at all. There are other errors that don't reference gles like these:
1>c:\glew-1.9.0\include\gl\glew.h(275): error C2371: 'GLdouble' : redefinition; different basic types
1> c:\qt\qt5.0.2\5.0.2\msvc2012_64\include\qtgui\qopengl.h(71) : see declaration of 'GLdouble'
1>c:\glew-1.9.0\include\gl\glew.h(630): warning C4005: 'GL_DOUBLE' : macro redefinition
1> c:\qt\qt5.0.2\5.0.2\msvc2012_64\include\qtgui\qopengl.h(68) : see previous definition of 'GL_DOUBLE'
1>c:\glew-1.9.0\include\gl\glew.h(1655): error C2371: 'GLintptr' : redefinition; different basic types
1> c:\qt\qt5.0.2\5.0.2\msvc2012_64\include\gles2\gl2.h(38) : see declaration of 'GLintptr'
1>c:\glew-1.9.0\include\gl\glew.h(1656): error C2371: 'GLsizeiptr' : redefinition; different basic types
1> c:\qt\qt5.0.2\5.0.2\msvc2012_64\include\gles2\gl2.h(39) : see declaration of 'GLsizeiptr'
1>c:\glew-1.9.0\include\gl\glew.h(1707): warning C4005: 'GL_BLEND_EQUATION_RGB' : macro redefinition
1> c:\qt\qt5.0.2\5.0.2\msvc2012_64\include\gles2\gl2.h(96) : see previous definition of 'GL_BLEND_EQUATION_RGB'
1>c:\glew-1.9.0\include\gl\glew.h(11533): warning C4005: 'GL_COVERAGE_SAMPLES_NV' : macro redefinition
1> c:\qt\qt5.0.2\5.0.2\msvc2012_64\include\qtgui\qopengles2ext.h(530) : see previous definition of 'GL_COVERAGE_SAMPLES_NV'
Hopefully you can help!
回答1:
My personal approach with using OpenGL with Qt is to separate all OpenGL related part from Qt class implementation. In the Qt part I then just call into the framework neutral written OpenGL code through regular C or C++ interfaces using standard types. Since the actual OpenGL code makes no references to Qt then, it doesn't have to include Qt headers, avoiding problems like yours.
回答2:
After a day of screwing around I have a solution!
In order to be cross platform Qt seems to have set OpenGLES to a high priority than desktop openGL.
THe solution to this is to build Qt from source code suing the setting -opengl desktop before you build. Something like this:
configure -debug-and-release -opengl desktop
Then use nmake to build and it works fine!
来源：https://stackoverflow.com/questions/17123100/glew-and-qt5-redefinition-of-headers